This is a revision of a competing renewal for the support of year 10 through 14 of our grant (AG 13396) concerned with phase shift tolerance in elderly people, previously considered by the MESH study section. This proposal is to determine whether there are possible adverse effects in a person's sleep and circadian rhythms resulting from the repeated phase shifts of shift work, which might carry over into retirement. We plan to study 800 retired men and women (65y+) with varying degrees of shift work exposure (200 in each of four bins: 1y-7y, 8y-14y, 15y-20y, >20y) during their working life, comparing them to 800 matched controls with zero exposure. We propose to use a 20-30 minute telephone survey of former shift workers to glean measures of sleep quality, circadian functioning, mental health and physical health which we will then relate to shift work exposure. In addition to questions related to demographics and shift work exposure, the interviews will include the following measures of sleep and circadian functioning: the Sleep Timing Questionnaire (STQ), the Pittsburgh Sleep Quality Index (PSQI), the sleep rigidity subscale of the Circadian Type Questionnaire (CTQ-Rs), and the Composite scale of Morningness-Eveningness (CSM). We shall also measure self-rated physical health and BMI, diabetes, caffeine consumption, and depressive symptomatology. One hundred of these 1600 subjects (20 in each of five matched shift work exposure bins: zero, 1y-7y, 8y-14y, 15y-20y, >20y), stratified by gender will then be studied in a 36h laboratory study in which sleep and circadian functioning will be assessed objectively using two nights of polysomnography, a salivary Dim Light Melatonin Onset (DLMO) assessment, and 36h of continuous core body temperature monitoring. Lifestyle regularity will be measured by the SRM-5 diary. Measures of physical health (history, physical, BMI, blood pressure), mental health (SCID), and functioning (SF-36, POMS) will also be taken from these 100 subjects. From both telephone survey and laboratory assessments, we shall test the hypothesis that prior years of shift work exposure increasingly lead to a dysfunction in sleep and circadian rhythm processes. Primary hypotheses to be tested by MANCOVA include: Subjects with higher shift work exposure will exhibit: more subjective sleep disruption, more irregular sleep timing, more extreme morningness-eveningness, more objective sleep disruption, abnormal DLMO and temperature rhythm phase, lower SRM-5 scores (lower lifestyle regularity) and reduced temperature rhythm amplitude. Secondary analyses will examine: mental and physical ill-health (including diabetes), BMI, blood pressure and Apnea- Hypopnea Index (AMI). In other secondary analyses we shall also examine the effects of temporal patterning of shift work over the lifespan, rotating versus fixed shifts and total number of night shifts worked. With the baby-boom generation is reaching retirement there will be an increase, not only in retired people in general, but also in retired people who have been working shift work schedules for many years. It is thus an important societal question as to whether such people will have sleep disorders and/or circadian dysfunction over and above those due simply to aging per se.